Separation of substances of interest from complex solutions has been accomplished via a variety of methods. Some applications include separation of biological substances of interest from a sample, such as, for example, purification of proteins from complex media such as fermentation broth. Such separations have been accomplished, among others, via cell clarification followed by column chromatography and the use of a fluidized bed of chromatographic media. These techniques suffer limitations, however, such as an inability to handle particulate matter and poor mass transfer, in the former, and short contact time, low capacity loading of the resin in the latter.
Magnetic separation is another means by which complex separations may be accomplished. In this context, biologically active magnetic particles in aqueous solution, termed magnetic fluids, have found particular use. The application of high gradient magnetic separation (HGMS), which uses a magnetic field to separate magnetic particles from suspension has been exploited such that when these particles are attached to biological materials of interest (e.g., cells, drugs), the material of interest or target material may thereby be separated from other materials not bound to the magnetic particles.
Several broad classes of magnetic fluids are known in the art, however presently use of each suffers limitations in its applicability. For example, surfactants can be used in a bilayer to form aqueous magnetic fluids, however, the fluids tend to destabilize on dilution, due to desorption of the outer surfactant layer, and methods to circumvent this have not been too successful, and moreover, are not easily amenable to scale up. Another class of magnetic fluids is that of single-polymer-coated magnetic fluids. These particles, however, are either too small for easy capture or are not stable in high ionic strength environments. Magnetic nanoparticles embedded in a polymer matrix, have also been used similarly, however, these particles are typically much larger and are not colloidally stable, requiring agitation to remain suspended, and possess a relatively low surface area.
An improved technology, without these limitations, and providing inexpensive, large-scale production of magnetic fluids would have broad application, yet at present, is lacking in the art.